What happens in your brain when you're mentally exhausted?

Have you ever felt as if your mind just wasn't working anymore after hours of intense concentration? That feeling of tiredness that goes beyond the physical - as if the act of thinking has become an effort? This could be a sign of mental fatigue.

This type of fatigue has become increasingly common, especially in routines that require constant focus. Mental fatigue goes beyond just being "tired": it involves drowsiness, difficulty concentrating, confused thoughts, slower reflexes and a drop in performance. As a result, even simple tasks can seem challenging.

But what is going on in our brain in this state? And does the brain react in the same way when we are at rest or in full mental activity? Science has been searching for these answers.

What science has discovered

Recent studies have used the electroencephalogram (EEG) - technology that measures brain waves - to better understand how mental fatigue manifests itself. In one of these studies, 20 participants underwent repetitive mental calculation activities, simulating a cognitive load similar to that of an ordinary day at work or study.

The researchers analyzed the participants' brain activity at two moments: while they were resting and while they were performing tasks - before and after they were mentally fatigued.

The result? The brain shows different signs of fatigue, depending on the context: being tired and trying to rest is different from being tired and trying to keep producing.

How does the brain react to fatigue?

The study analyzed different types of brain waves and what happens to them during fatigue. Here's what was observed:

• theta waves (related to sleepiness): increased in both states (at rest and on task), especially during tasks;
• alpha waves1 (linked to attention and the main indicator of mental fatigue): had a significant increase in both states, which indicates an effort to maintain focus, even when tired;
• alpha2 waves (associated with memory and cognitive functions): decreased during rest, but increased during activity, suggesting that more visual information is processed during activity;
• beta waves (related to mood and mental activity): showed a significant drop in both states, reflecting a lower ability to maintain mental rhythm.

These findings show that, even in the face of fatigue, the brain looks for strategies to keep working - such as increasing certain waves that help with attention and the execution of tasks. However, this comes at a cost: other functions, such as alertness and the ability to maintain mental rhythm, suffer. In other words, the brain even tries to compensate for the tirednessbut it can't keep all the gears turning with the same efficiency.

In addition, scientists have found that observing brain waves during rest can be even more effective at identifying fatigue than during activity.

Why does it matter to you?

Knowing how your brain responds to mental fatigue can help (a lot) to recognize the signs before they hinder your productivity or well-being.

If you're constantly feeling tired, having trouble concentrating or underperforming, perhaps it's time to rethink your routine, include adequate breaks and seek professional help.

 

Source: https://bmcneurosci.biomedcentral.com/articles/10.1186/s12868-020-00569-1